Bathroom Vanity Water Supply Lines

Bert spent 25 years working as a home-improvement and residential construction contractor in central Florida.

Two copper supply lines connect to this dual-port angle stop.

A quick trip to a local hardware store reveals many different types of faucet supply lines, sometimes called water supply tubes. Because the different styles are usually interchangeable, the supply line bought depends on the installer's preference. Each type has its own advantages and disadvantages. Some of the differences include the material type, cost, durability, and ease of installation.

The two 1/2" water pipes entering the cabinet below the sink supply water to a faucet. Hot water flows through the pipe on the left, and cold water passes through the pipe on the right. A set of water valves, usually angle stop valves, connect to the ends of the two pipes. The type of angle stop, and installation method, depend on the type of pipe. Most valves have 3/8-inch compression-thread discharge ports. A basic faucet has two 1/2-inch male pipe-thread—1/2 NPT—intake ports. A faucet supply line connects the valve's discharge port to the faucet intake port.

Some upgraded kitchen faucet models come with the water supply lines attached. Homes without angle stops use a centrally located manifold, often located in the garage, to isolate each water-using appliance. The pipes in these systems connect directly to the faucet with a nut and gasket.

A faucet, toilet, and refrigerator's ice maker use a similar water supply line. A refrigerator's ice maker uses 1/4-inch tubing with 1/4-inch compression fittings on both ends. A reducing fitting with 3/8- and 1/4-inch compression threads connect an ice maker's water supply line to a water valve with a 3/8-inch compression thread discharge port. A toilet connects to the angle stop valve with a 3/8-inch compression fitting, and the toilet's fill valve accepts a 7/8-inch threaded nut.

Before changing any type of faucet supply line, turn off the faucet's angle stop valve and turn on the faucet. After a short spurt of pressure, the water flow out of the faucet should quickly stop. This indicates that the angle stop valve has functioned properly. If the angle stop does not turn off the water to the faucet, turn off the home's water supply. If the building connects to city water, turn off the water at the water meter.

Professional plumbers usually use a curb key, sometimes called a meter key, to turn the meter's blade valve. However, it's often possible to turn the valve with a large adjustable wrench. If the building uses a well, turn off the well pump's circuit breaker. Consider replacing any leaking or malfunctioning angle stop valves while replacing the water supply line.

Use a tubing cutter to size copper and brass supply lines.

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Brass or Copper Supply Lines

Many buildings use plated brass or copper tubing for its faucet supply lines. Both types have a beveled discharge end, a long straight tube, and connect to the water valve with a compression nut and ring. As the nut tightens onto the valve, it presses the ring against the copper or brass tubing. This pressing action fills the void between the tubing's exterior and the discharge port, creating a watertight connection. A nut and washer hold the beveled end on the supply line against the bottom of the faucet's intake port.

This type of supply line has a long life expectancy. However, it requires special tools and skills to install properly. After adding the cost of the supply line, compression nut, and ring, the faucet nut and its washer this type of supply line become expensive.

Measure the distance between the valve's discharge port and the bottom of the faucet's corresponding intake port.
Add two inches to that measurement and cut the tubing to size with a copper-tubing cutter.
Using either a tubing bender or your hands, make slight bends to the tubing to achieve the correct bends. It is very important to avoid kinking the lines.
After each bend place the tubing in its place below the faucet. Use the tubing's placement as a visual reference for the next bend.
Try not to bend the last two inches on each end of the tubing. The tubing ends entering the faucet, and the shut-off valve must match the angle and placement of its respecting port.
Slip the faucet's locking nut, the compression nut, and ring over the small end of the supply tube.
Position the supply line in its proper place.
Tighten the supply tube to the faucet first, using a basin wrench to turn the nut clockwise.
Place one wrench on the water valve and a second wrench on the compression nut.
Hold the valve still and turn the compression nut clockwise.

Plastic or Vinyl Faucet Supply Lines

Many homes have rigid plastic or vinyl faucet supply lines. This type of supply line uses the same installation method as brass or copper tubing. It is the cheapest of all the supply line options; however, they tend to fail quicker than the other types. A plastic or vinyl supply line uses a plastic compression ring. A plastic ring will not cut the supply line as the compression nut tightens, while a brass ring can gouge the supply line. The faucet nuts are available in both plastic and metal.

Measure the distance between the angle stop valve's discharge port and the bottom of the corresponding faucet intake port. Add a couple of inches to the measurement; the exact amount of extra depends on the supply line's route.
Cut the tubing to size at the appropriate spot with either a copper-tubing cutter or a ratchet-style PVC cutter.
Slip the faucet's locking nut, the compression nut, and the plastic ring over the small end of the supply tube.
Position the supply line's beveled end against the bottom of the faucet's intake port. Hand tightens the faucet locking nut.
Bend the tubing until its other end lines up with the angle stop's discharge port. Trim the end of the tubing as needed.
Carefully place the end of the plastic tubing in the valve's discharge port. Position the ring and nut against the discharge port. Hand tightens the nut.
Tighten the supply line's faucet nut with a basin wrench. A basin wrench has a long handle and uses swiveling jaws to grab the nut.
Place one adjustable wrench on the water valve and a second adjustable wrench on the compression nut.
Hold the valve still and turn the compression nut clockwise.

A standard residential faucet supply line has a 3/8-inch compression fitting on one end and a 1/2-inch female NPT fitting on the other.

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Flexible Faucet Supply Lines

Because of their trouble-free nature, most homeowners choose to install flexible supply lines. A flexible supply line has either a braided stainless steel or vinyl sleeve. A flexible supply line comes with the faucet locking nut and compression nut attached.

These supply lines use rubber washers to seal the connections. Some upgraded supply lines have a sensor attached to the valve connection. If this sensor detects a sudden water pressure loss, the sensor turns off an emergency valve in the supply line. These supply lines are easy to install and last a long time. However, they are the most expensive type of faucet supply line.

Measure the distance between the water valve and the faucet intake ports.
Buy a faucet supply line at least an inch longer than the measurement. This type of supply line comes from the manufacturer in standard lengths: typically 12, 16, 20 and 30 inches. Supply line extensions come with one 3/8-inch female and male end.
Connect the extension's male end to the short faucet supply line's 3/8-inch female fitting.
Hand tightens the supply line's faucet nut against the faucet's intake port.
Turn the locking nut one full turn clockwise with a basin wrench.
Hand tighten the supply line's compression nut on the valve's discharge port. If the supply line is too long, create a large loop in the supply line before attaching the compression nut. Use care to avoid kinking the tube.
Hand tighten the compression nut.
Place one wrench on the water valve and the second wrench on the compression nut.
Hold the valve still and turn the compression nut one full turn clockwise.

This article is accurate and true to the best of the author's knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: Is pressure reduced in a 1/2 to 3/8 inch supply line ?

Answer: With the faucet closed, the static pressure will remain the same. The faucet's valve or cartridge ports are smaller than either tubing sizes. So, even with the faucet open, the pressure should remain relatively the same.

Question: My existing copper/brass water supply lines are too long for new bathroom faucet intake ports. How bendable are the intake lines?

Answer: They will bend. However, it is very difficult to do this without kinking the lines. In most cases, it makes sense to remove the tubing and cut it to size. This avoids undue stress on the plumbing pipes coming out of the wall. Also, to avoid a leak the faucet connection must line up with the supply tube perfectly.

bibio on January 18, 2018:

thank you ,now i know, i never call a plumber again

Bathroom Vanity Water Supply Lines

Source: https://dengarden.com/home-improvement/Faucet-Supply-Line-Types-and-Installation

Bathroom Vanity Water Supply Lines